Multi-pair aggregate power distribution

ABSTRACT

Apparatus and method for transmitting over non-adjacent multiple conducting pairs and aggregating powers from the conducting pairs to power remote electronic devices at an end station include, at a line termination (LT), a plurality of power transmitting circuits configured to transmit power over the multiple conducting pairs, and a microcontroller coupled to the plurality of power transmitting circuits and configured to receive a current sense signal from a power receiving circuit at the remote electronic device, and further include, at a network termination (NT), one or more current limiters coupled to multiple conducting pairs and operable to limit the power from the conducting pairs based on power demand information of the end station, and a load controller coupled to the one or more current limiters and configured to selectively activate the one or more current limiters based on a determination by the microcontroller that the end station is allowed to receive a full power demand, the determination being a function of a demand current profile of the end station.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 10/287,886 filed Nov. 4, 2002 now U.S. Pat. No. 7,053,501entitled “Multi-Pair Aggregate Power Distribution,” all commonly ownedherewith.

FIELD OF THE INVENTION

The present invention relates generally to electrical powerdistribution. More particularly, the present invention relates tomethods of and apparatuses for transmitting and aggregating power overmultiple conducting pairs to remote devices.

BACKGROUND OF THE INVENTION

For many years conventional telephone handsets have been powered from acentral office (CO) or a wiring closet of a private branch exchange(PBX). Power from the CO is supplied over the same twisted pair as isused for voice communication between the CO and the handset. In otherwords, the power distribution and voice communication medium comprises asingle twisted pair within the PSTN (public switched telephone network).Because conventional telephone handsets are powered independent of theelectrical power grid, they are able to continue functioning even whenpower on the electrical power grid is disrupted, for example as mayhappen due to a power outage.

It would be desirable to extend the advantage of electrical powerindependency to modem telephonic devices such as, for example, IP(Internet Protocol) telephones or IEEE 802.11 access points. (IEEE is anacronym for Institute of Electrical and Electronics Engineers; 802.11 isa wireless local area network standard set by the IEEE.) However, due tothe relatively larger power demands of such devices, regulatory limitson the power that may be transmitted over PSTN twisted pair cabling, andthe high resistance of PSTN twisted pairs (which can be up to 1300 Ω or250 Ω/km for a given pair), solutions to extend the advantage have notbeen feasible.

Power over other types of transmission media has been addressed. Forexample, “Power over LAN (Local Area Network)”, known in the industry asthe IEEE 802.3af standard, specifies distributing power over Ethernetcabling to remote devices on a LAN. So, in a LAN environment IPtelephones may be powered independently of the status of the electricalpower grid. Among other specifications of the 802.3af standard, powermay be delivered over two adjacent pairs of a Category 5 cable to aremote device by applying a common mode voltage on each pair and usingthe differential between the pairs to deliver the power. This use of twoadjacent pairs permits additional power to be distributed to a remotedevice that may require more power than can be delivered over a singlecable pair.

Because of the problems of transmitting power over the PSTN (publicswitched telephone network), and to the PSTN, e.g., private branchexchange (PBXs), however, DSL (digital subscriber line) and DSL-likedevices are not within the scope of the 802.3af standard. A principlereason for this is that traditional DSL operates over the PSTN and atlong distances and, therefore, does not provide an efficient or evenfeasible means for transmitting power to a remote device. DSL devicestypically require more power than a PSTN conducting pair is capable ofcarrying or is permitted to carry due to regulatory concerns. Indeed, inmost instances the PSTN pair used for traditional DSL is not even ableto carry the current that would be necessary to power the DSL interfaceof a DSL device, not to mention the current that would be required topower the remaining technology making up the DSL device.

At the expense of reach for increased data rates, a newer technologyreferred to as Long-Reach Ethernet or VDSL (Very High Bit Rate DSL)technology uses shorter cabling distances than traditional DSL, e.g.,less than about 1.5 km compared to less than about 3.7 km fortraditional ADSL (Asynchronous Digital Subscriber Line) technology.Because VDSL uses shorter cabling distances, distributing power over asingle twisted pair to a remote DSL device, IP telephone or other remotedevice, becomes a near possibility. Unfortunately, however, thedistances are still too great for most applications, particularly at themaximum reach of VDSL. To increase the power reach, one solution mightbe to use two adjacent twisted pairs to distribute power, e.g., in amanner analogous to that which may be done to transmit power overEthernet cabling according to the IEEE 802.3af Power over LAN standard.However this approach is not practicable since adjacent pairs of a DSLsystem from the wiring closet or CO, i.e., from the line termination(LT) of the system, are arbitrarily routed so that there is no guaranteethat they maintain their adjacency at the network termination (NT) ofthe system.

SUMMARY OF THE INVENTION

The present invention is directed at methods of and apparatuses fortransmitting and aggregating power over multiple conducting pairs toremote devices.

According to an aspect of the present invention, a system for providingpower to electronic devices comprises a wiring closet having powersupplying capabilities for providing power to a plurality of conductingpairs and a remote termination adapted to aggregate power provided toand transmitted by two or more non-adjacent pairs of the plurality ofconducting pairs and supply the aggregated power to a remote electronicdevice.

According to another aspect of the present invention, a system forproviding power to electronic devices comprises a wiring closet having aplurality of power circuits configured to transmit power over aplurality of conducting pairs. First and second pairs of the pluralityof conducting pairs are routed to a first remote location for providingan aggregated power to a first remote device. The first pair isnon-adjacent to the second pair at a line termination (LT) end of thesystem.

According to yet another aspect of the present invention, a method ofproviding power to an electronic device comprises coupling an electronicdevice to first and second conducting pairs, the first and secondconducting pairs being non-adjacent conducting pairs provided by awiring closet or central office, applying power to the first and secondconducting pairs, limiting a current drawn through the first and secondconducting pairs to a predetermined limited current, sensing thepredetermined limited current drawn by the electronic device,determining a current demand of the electronic device, based on thepredetermined limited current drawn by the electronic device, andpermitting the current demand of the electronic device to increase to afull demand, so long as the current demand does not exceed a maximumcurrent carrying limit of the first and second conducting pairs.

Other aspects of the inventions are described and claimed below, and afurther understanding of the nature and advantages of the inventions maybe realized by reference to the remaining portions of the specificationand the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary power distribution system, according to anembodiment of the present invention;

FIG. 2 shows an exemplary power circuit for producing AC power, whichmay be used to transmit power to a conducting pair in the system shownin FIG. 1, according to an embodiment of the present invention;

FIG. 3 shows elements of an exemplary power distribution system at theLT end of the system in FIG. 1, according to an embodiment of thepresent invention;

FIG. 4A shows elements of an exemplary power distribution system at theNT end of the system in FIG. 1, according to an embodiment of thepresent invention;

FIG. 4B shows an exemplary current demand profile of an end station inFIG. 4A, according to an embodiment of the present invention;

FIG. 5A shows salient steps of an exemplary process for adding a deviceto a system like that shown in FIG. 1, from the perspective of the LT ofthe system, according to an embodiment of the present invention; and

FIG. 5B shows salient steps of an exemplary process for adding a deviceto a system like that shown in FIG. 1, from the perspective of the NT ofthe system, according to an embodiment of the present invention.

The disclosure contains, by necessity, simplifications, generalizationsand omissions of detail. Consequently, those skilled in the art willappreciate that the disclosure is illustrative only and is not intendedin any way to be limiting.

DETAILED DESCRIPTION

Those of ordinary skill in the art will realize that the followingdetailed description of the present invention is illustrative only andis not intended to be in any way limiting. Other embodiments of thepresent invention will readily suggest themselves to such skilledpersons having the benefit of this disclosure.

Embodiments of the present invention are described herein in the contextof methods of and apparatuses for using multiple conducting pairs totransmit power to remote electronic devices. While not expressly shownin the drawings, one skilled in the art will understand that theconducting pairs over which power is transmitted to the various remotedevices may also be used to for communicating data and voice informationto/from the remote devices. Reference will now be made in detail toimplementations of the present invention as illustrated in theaccompanying drawings. The same reference indicators will be usedthroughout the drawings and the following detailed description to referto the same or like parts.

Referring to FIG. 1, there is shown a power distribution system 10,according to an embodiment of the present invention. A central office(CO) or wiring closet 100 (e.g. of a private branch exchange (PBX)) islocated at a line termination (LT) end of system 10. CO/wiring closet100 provides a plurality of conducting pairs 102, which are identifiedin FIG. 1 as pair 1, pair 2, pair 3, pair 4, pair 5, pair (M−1) and pairM. Here, M is an integer that is greater than or equal to two.Conducting pairs 102 are arbitrarily configured between the LT and oneor more end stations, which are identified in FIG. 1 as end station #1,end station #2, . . . end station #N. Here, N is an integer greater thanor equal to one. End stations #1, #2, . . . #N represent either a remoteelectronic device or a remote location at which an electronic device maybe coupled to the conducting pairs.

According to the first alternative, end stations #1, #2, . . . #N mightcomprise, for example, any combination of IP (Internet Protocol)telephones, wireless access points (e.g. conforming to standards such asIEEE 802.11, Bluetooth, etc.), DSL (Digital Subscriber Line) modems,DSL-like devices, communication repeaters for conditioning data or voicesignals, etc. In the last example, a repeater would not technicallycomprise an “end” station. Rather, such a device would be moreaccurately identified as an intermediate device coupled between the LTand the NT. Nevertheless, those skilled in the art would readilyunderstand that any one or more of the “end stations #1, #2, . . . #N”may comprise a communication repeater, with the understanding that theconditioned data and/or voice signals are operable to transmit andreceive data and/or voice signals to/from a true remote end station notshown in FIG. 1. According to the latter alternative, end stations #1,#2, . . . #N might comprise, for example, hotel rooms of a hotel,different rooms or buildings of a business campus, different residencesin a residential service area, etc., within which an electronic devicemay be coupled to the available conducting pairs. The conducting pairs(i.e. pair 1, pair 2, . . . pair (M−1) and pair M) may comprise shieldedor unshielded twisted pair wires of a private branch exchange (PBX) orthe public switched telephone network (PSTN), Category 5 cables, orother conducting pair technology.

According to an exemplary embodiment of the present invention, forexample where conducting pairs 102 comprise twisted pairs of a PBX orPSTN, conducting pairs 102 are pre-routed, i.e., are permanently andunalterably configured between CO/wiring closet 100 and end stations #1,#2, . . . #N. This is illustrated in FIG. 1, where non-adjacent pair 1and pair 3 are routed to end station #1, adjacent pairs M and (M−1) arerouted to end station #2 and pairs 2, 4, and 5 (pair 4 being adjacent topair 5 and pair 2 being non-adjacent to pairs 4 and 5) are routed to endstation #N. Pairs of other relationships (e.g. number and adjacency ornon-adjacency) not shown in FIG. 1 may also be possible. As explained inmore detail below, power is distributed over conducting pairs 102, sothat the remote devices at the NT may be supplied with power and,therefore, maintain their operation independent and exclusive of theelectrical power grid.

At the LT of system 10, each conducting pair of the plurality ofconducting pairs 102 is coupled to a power circuit 20, which selectivelysupplies power to its associated conducting pair. In one embodiment thepower may be transmitted as direct current (DC). In another embodimentthe power is transmitted as alternating current (AC). FIG. 2 shows anexemplary power circuit 20 for producing AC power, which may be used totransmit power to a conducting pair. Power circuit 20 is configured as aswitched mode power supply, which produces an AC pulse train by“chopping” a DC power supply, Vsupp, by the opening and closing of ahigh power switching transistor 200. The opening and closing ofswitching transistor 200 is controlled by a gate control signal 202,optionally buffered by a buffer 204. A resistor 212 is shown coupled tothe transistor 200 in the embodiment in FIG. 2. The frequency of gatecontrol signal 202 is set to a low enough frequency so that it and thegenerated AC power do not interfere with data and or voice signals thatmay be communicated over the same conducting pair. A triple-woundtransformer having a primary coil 206, a secondary coil 208 and acurrent sense coil 210 is wound to provide the desired AC voltage to theconducting line pair. In the embodiment shown in FIG. 2, a capacitor 216is coupled across the line pair. Current sense coil 210 mirrors thecurrent and voltage induced through and across secondary coil 208 and,as explained in more detail below, is used to provide a sense line to apower controller to regulate the current and voltage supplied to thepair. In the embodiment shown in FIG. 2, a diode 214 is coupled to thecurrent sense coil 210. It should be emphasized here that power circuit20 is only one of many AC power generators that can be used to provideAC power to a conducting pair. For example, a power circuit thatgenerates sine waves may alternatively be used for greater efficiencyand reduced power loss, but with added complexity and cost. Accordingly,those skilled in the art will readily appreciate that the power circuitshown in FIG. 2 is only exemplary and is but one of many possible powergenerating and sensing circuits.

Referring now to FIG. 3, there is shown an exemplary embodiment of theelements of a power distribution system at the LT end of the system,according to an embodiment of the present invention. A plurality ofpower/sense circuits, identified in FIG. 3 as power/sense circuit #1,power circuit #2, . . . power circuit #M, are correspondingly coupled topair #1, pair #2, pair #M. Each power/sense circuit #1, #2, . . . #M maycomprise the exemplary power circuit 20 shown in FIG. 2 or similarpower/sense circuit. Power/sense circuits #1, #2, . . . #M selectivelyprovide power to their corresponding conducting pairs #1, #2 and #M, asexplained in more detail below. Gate control lines, identified in FIG. 3with the label “gate”, are coupled between a microcontroller 300 andpower/sense circuits #1, #2, . . . #M. Sense lines, identified in FIG. 3with the label “sense”, are also coupled between microcontroller 300 andpower/sense circuits #1, #2, . . . #M. As explained in more detailbelow, microcontroller 300 uses sense signals from the sense lines toregulate the voltage and current supplied to the conducting pairs. Thisregulation may be accomplished, at least in part, by microcontroller 300altering characteristics of gate control signals sent over the gatecontrol lines to the power/sense circuits #1, #2, . . . #M.

Referring now to FIG. 4A, there is shown an exemplary embodiment of theelements of a power distribution system at the NT end of the system,according to an embodiment of the present invention. The exemplaryembodiment correlates with the exemplary power distribution system 10shown in FIG. 1 so that end station #N and its associated pairs at theNT in FIG. 4A correspond to end station #N and associated pairs, pair#2, pair #4 and pair #5, at the LT in FIG. 1. FIG. 4A illustrates howthe currents transmitted over conducting pairs #2, #4 and pair #5 areaggregated at the NT end to provide an aggregated current to power endstation #N. In the embodiment shown in FIG. 4A, a capacitor 416 iscoupled across the input into the power end station #N. Poweraggregation to other end stations is similar to that shown.

Each of the pairs #2, #4 and #5 are coupled to a correspondingrectifier. Accordingly, rectifiers 402, 404 and 405 in FIG. 4A arecoupled to pairs #2, #4 and #5, respectively, and are operable torectify the AC power received over the pairs. Rectifiers 402, 404 and405 are coupled to inputs of current limiters 408, 410 and 412, whichare individually controlled by a load controller 414 (which maycomprise, for example, a microcontroller). As explained in more detailbelow, load controller 414 limits the current sourced from thepower/sense circuits at the LT end and which may be sunk by end station#N, until it is determined that pairs #2, #4 and #5 are capable oftransmitting the power needs of end station #N. By controlling thecurrent draw of end station #N as the conducting pairs #2, #4 and #5 arefirst coupled to the NT, the microcontroller at the LT can determinewhat the current demand requirements (e.g. what power class of device)are at end station #N.

Referring to FIG. 4B, there is shown an exemplary current demand profileof end station #N in FIG. 4A, once conducting pairs #2, #4 and #5 arecoupled to the NT (i.e., once end station #N is coupled to the powerdistribution system 10). When end station #N is first coupled to powerdistribution system 10, via pairs #2, #4 and #5, load controller 414controls line control limiters 408, 410 and 412 so that the aggregatedcurrent drawn by end station #N is limited to a predetermined limitedcurrent level, I(limit), as shown in FIG. 4B. While limited to I(limit),the sense lines of power/sense circuits #2, #4 and #5 at the LT endsignal the current demand profile information of end station #N tomicrocontroller 300. From the sensed current demand profile, themicrocontroller at the LT end determines whether the device is inregulatory compliance and whether power/sense circuits #2, #4 and #5 areable to supply the current demanded by end station #N when operating atfull demand. As described in more detail below, the magnitude and/orduration Δt of the predetermined limited current level I(limit) aredesigned so that the necessary time and current demand information areavailable for the microcontroller at the LT to perform its screening andregulating functions. With certain exceptions described in detail below,if the microcontroller at the LT determines that end station #N is inregulatory compliance and power/sense circuits #2, #4 and #5 are able tosource the maximum current that could be demanded by end station #N,controller 414 switches off current limiters 408, 410 and 412 and allowsthe device to begin sourcing the current required for fullfunctionality. This current is shown in FIG. 4B as I(full demand). Inone embodiment, the microcontroller at the LT regulates power/sensecircuits #2, #4 and #5 so that the current draw is distributed evenlyamong pairs #2, #4 and #5.

FIGS. 5A and 5B show an exemplary process of adding an electronic deviceto the system and selectively providing power to the device overmultiple conducting pairs, according to embodiment of the presentinvention. FIG. 5A shows the salient steps of the process at the LT ofthe system and FIG. 5B shows the salient steps of the process at the NTof the system. Both are explained below.

Referring first to FIG. 5A, at step 500 a voltage of a predeterminedvalue is applied to multiple conducting pairs at the LT, which have beenpre-routed to a remote destination at the NT where an electronic deviceis to be coupled to the conducting pairs. At step 502 the electronicdevice is coupled to the multiple conducting pairs. (This step mayoptionally be performed prior to step 500.) At step 504 current drawnthrough each pair is sensed in a manner similar to or the same as thatdescribed above. As explained below, at this stage in the process thecurrent drawn by the electronic device is limited to a predeterminedvalue. Based on the current profile of the current drawn, at step 506the microcontroller at the LT determines the current demand requirementsof the electronic device.

Next, at step 508 the microcontroller determines whether the powercircuits providing power to the conducting pairs are allowed to deliverthe required current demand of the end device. This determinationdepends on the satisfying of four criteria. First, the power/sensecircuits themselves must be capable of delivering the maximum currentwhich the device may demand. Second, the multiple conducting pairs mustbe physically capable of carrying the full current demand of theelectronic device. Third, the power transmitted over the conductingpairs must comply with regulatory standards. Finally, addition of theelectronic device must not result in the main power supply of the system(i.e. Vsupp) exceeding its current supplying capabilities to all powercircuits at the LT. The last requirement results from the power/sensecircuits being powered from a main power supply, Vsupp. Vsupp is limitedin how much total current the system 10 may provide to remote devices.As devices are added to the power distribution system, microcontroller300 records the combined load of all configured devices and compares itto a maximum allowable current that may be drawn from Vsupp. If adding anew device would result in the system current exceeding the maximumallowable current that may be supplied by Vsupp, the microcontroller atthe LT will not permit power to be distributed over any pairs coupled tothe device. If the microcontroller at the LT determines that the allfour criteria described above can be satisfied, at step 512 current fromthe power circuits is permitted to increase to full demand, over therespective conducting pairs and to the remote device. If any of the fourcriteria is not satisfied, at step 510 all voltages applied to theconducting pairs routed to the device, which is attempting to connect tothe system, are withdrawn. Other pairs providing power to other endstations are not affected by this step. It should be emphasized herethat the apparatus and criteria used to determine whether to allowcurrent to increase to full demand described above are only exemplary.Other embodiments may use different criteria or may use further criteriasuch as, for example, temperature as a basis for the decision.

FIG. 5B show the salient steps of the process of adding an electronicdevice to the system and selectively providing power to the device overmultiple conducting pairs, from the perspective of the NT of the system,according to an embodiment of the present invention. At step 514 anypower sources applied to the conducting pairs to which the electronicdevice is to be coupled are decoupled from the pairs. Next, at step 516(which corresponds to step 502 in FIG. 5A) the device is coupled to theconducting pairs routed to the remote destination at which the device isbeing coupled to the system. As soon as the device is coupled to theconducting pairs, at step 518 controller 414 limits the current drawn bythe device to a predetermined current limit, I(limit), in a mannersimilar to or the same as that described above. Following a timeduration Δt, at step 520 the current limits are removed and the deviceis allowed to increase its current draw to its full demand. The durationof Δt is set so that it expires after the time it would be required tocomplete step 504 in FIG. 5A. Accordingly, if at step 508 in FIG. 5A itis determined that the system cannot (or is not permitted to) supplycurrent to the device, power is removed from the conducting pairs atstep 514 in FIG. 5A and current is never allowed to increase to fulldemand at step 520. If, on the other hand, Δt expires without powerbeing removed from the conducting pairs, once controller 414 removes thecurrent limiting condition, current drawn by the device increasesaccording to its demand. It should be emphasized here that the methodsdescribed in FIGS. 5A and 5B are but one way of signaling NT powerrequirements. Accordingly, those skilled in the art will readilyunderstand that other methods and apparatus for sensing and limitingcurrent may be employed without departing from the spirit and scope ofthe invention.

In addition to the processing steps described in FIGS. 5A and 5B, themicrocontroller at the LT of the system monitors and regulates thecurrent supplied over the plurality of conducting pairs 102 at all timesto ensure that the max current and voltage are not exceeded. If at anytime the current through or voltage across a pair (or pairs) exceeds aregulatory or design limit, power to that pair or pairs is removed.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art that,based upon the teachings herein, changes and modifications may be madewithout departing from this invention and its broader aspects.Therefore, the appended claims are intended to encompass within theirscope all such changes and modifications as are within the true spiritand scope of this invention.

1. A system for providing power from a line termination (LT) to an endstation at a network termination (NT), the system comprising: aplurality of power transmitting circuits at the LT configured totransmit power over a plurality of conducting pairs; a power receivingcircuit at the NT configured to receive power from any two or moreselected conducting pairs of the plurality of conducting pairs, whereinthe power receiving circuit is configured to provide aggregated powerfrom the two or more conducting pairs to the end station; amicrocontroller at the LT coupled to the plurality of power transmittingcircuits, wherein the microcontroller is configured to receive a currentsense signal from the power receiving circuit; one or more currentlimiters coupled to the first and second conducting pairs, the one ormore current limiters operable to limit the power from the first andsecond conducting pairs based on power demand information of the endstation; and a load controller coupled to the one or more currentlimiters, wherein the load controller selectively activates the one ormore current limiters based on a determination by the microcontrollerthat the end station is allowed to receive a full power demand, saiddetermination being a function of a demand current profile of the endstation.
 2. The system of claim 1 wherein a first conducting pair and asecond conducting pair of the two or more conducting pairs arenon-adjacent to one another.
 3. The system of claim 1 wherein the powerreceiving circuit further comprises one or more rectifiers configured toreceive AC power transmitted over the first and second conducting pairsand configured to rectify the AC power into direct current (DC) power.